Genetically modified maize

Genetically modified maize (corn) is a genetically modified crop. Specific maize strains have been genetically engineered to express agriculturally-desirable traits, including resistance to pests and to herbicides. Maize strains with both traits are now in use in multiple countries. GM maize has also caused controversy with respect to possible health effects, impact on other insects and impact on other plants via gene flow. One strain, called Starlink, was approved only for animal feed in the US, but was found in food, leading to a series of recalls starting in 2000.

Corn varieties resistant to glyphosate herbicides were first commercialized in 1996 by Monsanto, and are known as "Roundup Ready Corn". They tolerate the use of Roundup.[1]Bayer CropScience developed "Liberty Link Corn" that is resistant to glufosinate.[2]Pioneer Hi-Bred has developed and markets corn hybrids with tolerance to imidazoline herbicides under the trademark "Clearfield" - though in these hybrids, the herbicide-tolerance trait was bred using tissue culture selection and the chemical mutagen ethyl methanesulfonate not genetic engineering.[3] Consequently, the regulatory framework governing the approval of transgenic crops does not apply for Clearfield.[3]

As of 2011, herbicide-resistant GM corn was grown in 14 countries.[4] By 2012, 26 varieties herbicide-resistant GM maize were authorised for import into the European Union.[5] In 2012 the EU was reported to import 30 million tons a year of GM crops, but such imports remain controversial.[6] Cultivation of herbicide-resistant corn in the EU provides substantial farm-level benefits.[7]

In recent years, traits have been added to ward off Corn ear worms and root worms, the latter of which annually causes about a billion dollars in damages.[11][12]

The Bt protein is expressed throughout the plant. When a vulnerable insect eats the Bt-containing plant, the protein is activated in its gut, which is alkaline. In the alkaline environment the protein partially unfolds and is cut by other proteins, forming a toxin that paralyzes the insect's digestive system and forms holes in the gut wall. The insect stops eating within a few hours and eventually starves.[13]

In 1996, the first GM maize producing a Bt Cry protein was approved, which killed the European corn borer and related species; subsequent Bt genes were introduced that killed corn rootworm larvae.[14]

In 2013 Monsanto launched the first transgenic drought tolerance trait in a line of corn hybrids called DroughtGard.[18] The MON 87460 trait is provided by the insertion of the cspB gene from the soil microbe Bacillus subtilis; it was approved by the USDA in 2011[19] and by China in 2013.[20]

The theory behind these refuges is to slow the evolution of resistance to the pesticide. EPA regulations also require seed companies to train farmers how to maintain refuges, to collect data on the refuges and to report that data to the EPA.[23] A study of these reports found that from 2003 to 2005 farmer compliance with keeping refuges was above 90%, but that by 2008 approximately 25% of Bt corn farmers did not keep refuges properly, raising concerns that resistance would develop.[23]

Unmodified crops received most of the economic benefits of Bt corn in the US in 1996-2007, because of the overall reduction of pest populations. This reduction came because females laid eggs on modified and unmodified strains alike.[24]

Resistant strains of the European corn borer have developed in areas with defective or absent refuge management.[24][25]

In November 2009, Monsanto scientists found the pink bollworm had become resistant to first-generation Bt cotton in parts of Gujarat, India - that generation expresses one Bt gene, Cry1Ac. This was the first instance of Bt resistance confirmed by Monsanto anywhere in the world.[26][27] Bollworm resistance to first generation Bt cotton has been identified in the Australia, China, Spain and the United States.[28] In 2012, a Florida field trial demonstrated that army worms were resistant to pesticide-containing GM corn produced by Dupont-Dow; armyworm resistance was first discovered in Puerto Rico in 2006, prompting Dow and DuPont to voluntarily stop selling the product on the island.[29]

Broad scientific consensus holds that food derived from GM crops poses no greater risk to human health than conventional food.[32][33][34][35][36][37] The scientific rigor of the studies regarding human health has been disputed due to alleged lack of independence and due to conflicts of interest involving governing bodies and some of those who perform and evaluate the studies.[38][39][40][41]

GM crops provide a number of ecological benefits, but there are also concerns for their overuse, stalled research outside of the Bt seed industry, proper management and issues with Bt resistance arising from their misuse.[41][42][43]

Critics have objected to GM crops on ecological, economic and health grounds. The economic issues derive from those organisms that are subject to intellectual property law, mostly patents. The first generation of GM crops lose patent protection beginning in 2015. Monsanto has claimed it will not to pursue farmers who retain seeds of off-patent varieties.[44] These controversies have led to litigation, international trade disputes, protests and to restrictive legislation in most countries.[45]

Critics claim that Bt proteins could target predatory and other beneficial or harmless insects as well as the targeted pest. These proteins have been used as organic sprays for insect control in France since 1938 and the USA since 1958 with no ill effects on the environment reported.[8] While cyt proteins are toxic towards the insect orders Coleoptera (beetles) and Diptera (flies), cry proteins selectively target Lepidopterans (moths and butterflies). As a toxic mechanism, cry proteins bind to specific receptors on the membranes of mid-gut (epithelial) cells, resulting in rupture of those cells. Any organism that lacks the appropriate gut receptors cannot be affected by the cry protein, and therefore Bt.[46][47] Regulatory agencies assess the potential for the transgenic plant to impact nontarget organisms before approving commercial release.[48][49]

A 1999 study found that in a lab environment, pollen from Bt maize dusted onto milkweed could harm the monarch butterfly.[50][51] Several groups later studied the phenomenon in both the field and the laboratory, resulting in a risk assessment that concluded that any risk posed by the corn to butterfly populations under real-world conditions was negligible.[52] A 2002 review of the scientific literature concluded that "the commercial large-scale cultivation of current Bt–maize hybrids did not pose a significant risk to the monarch population".[53][54][55] A 2007 review found that "nontarget invertebrates are generally more abundant in Bt cotton and Bt maize fields than in nontransgenic fields managed with insecticides. However, in comparison with insecticide-free control fields, certain nontarget taxa are less abundant in Bt fields."[56]

Gene flow is the transfer of genes and/or alleles from one species to another. Concerns focus on the interaction between GM and other maize varieties in Mexico, and of gene flow into refuges.

In 2009 the government of Mexico created a regulatory pathway for genetically modified maize,[57] but because Mexico is the center of diversity for maize, gene flow could affect a large fraction of the world's maize strains.[58][59] A 2001 report in Nature presented evidence that Bt maize was cross-breeding with unmodified maize in Mexico.[60] The data in this paper was later described as originating from an artifact. Nature later stated, "the evidence available is not sufficient to justify the publication of the original paper".[61] A 2005 large-scale study failed to find any evidence of contamination in Oaxaca.[62] However, other authors also found evidence of cross-breeding between natural maize and transgenic maize.[63]

The French High Council of Biotechnologies Scientific Committee reviewed the 2009 Vendômois et al. study and concluded that it "..presents no admissible scientific element likely to ascribe any haematological, hepatic or renal toxicity to the three re-analysed GMOs."[65] However, the French government applies the precautionary principle with respect to GMOs.[citation needed]

A review by Food Standards Australia New Zealand and others of the same study concluded that the results were due to chance alone.[66][67]

A 2011 Canadian study looked at the presence of CryAb1 protein (BT toxin) in non-pregnant women, pregnant women and fetal blood. All groups had detectable levels of the protein, including 93% of pregnant women and 80% of fetuses at concentrations of 0.19 ± 0.30 and 0.04 ± 0.04 mean ± SD ng/ml, respectively.[68] The paper did not discuss safety implications or find any health problems. The paper was found to be unconvincing by multiple authors and organizations.[69][70][71] In a swine model, Cry1Ab-specific antibodies were not detected in pregnant sows or their offspring and no negative effects from feeding Bt maize to pregnant sows were observed.[72]

In January 2013, the European Food Safety Authority released all data submitted by Monsanto in relation to the 2003 authorisation of maize genetically modified for glyphosate tolerance.[73]

StarLink contains Cry9C, which had not previously been used in a GM crop.[74] Starlink's creator, Plant Genetic Systems had applied to the US Environmental Protection Agency (EPA) to market Starlink for use in animal feed and in human food.[75]:14 However, because the Cry9C protein lasts longer in the digestive system than other Bt proteins, the EPA had concerns about its allergenicity, and PGS did not provide sufficient data to prove that Cry9C was not allergenic.[76]:3 As a result PGS split its application into separate permits for use in food and use in animal feed.[74][77] Starlink was approved by the EPA for use in animal feed only in May 1998.[75]:15

StarLink corn was subsequently found in food destined for consumption by humans in the US, Japan, and South Korea.[75]:20–21 This corn became the subject of the widely publicized Starlink corn recall, which started when Taco Bell-branded taco shells sold in supermarkets were found to contain the corn. Sales of StarLink seed were discontinued.[78][79] The registration for Starlink varieties was voluntarily withdrawn by Aventis in October 2000. (Pioneer had been bought by AgrEvo which then became Aventis CropScience at the time of the incident,[75]:15–16 which was later bought by Bayer[80]

Fifty-one people reported adverse effects to the FDA; US Centers for Disease Control (CDC), which determined that 28 of them were possibly related to Starlink.[81] However, the CDC studied the blood of these 28 individuals and concluded there was no evidence of hypersensitivity to the Starlink Bt protein.[82]

A subsequent review of these tests by the Federal Insecticide, Fungicide, and Rodenticide Act Scientific Advisory Panel points out that while "the negative results decrease the probability that the Cry9C protein is the cause of allergic symptoms in the individuals examined ... in the absence of a positive control and questions regarding the sensitivity and specificity of the assay, it is not possible to assign a negative predictive value to this."[83]

The US corn supply has been monitored for the presence of the Starlink Bt proteins since 2001.[84]

In 2005, aid sent by the UN and the US to Central American nations also contained some StarLink corn. The nations involved, Nicaragua, Honduras, El Salvador and Guatemala refused to accept the aid.[85]

On December 19, 2013 six Chinese citizens were indicted in Iowa on charges of plotting to steal genetically modified seeds worth tens of millions of dollars from Monsanto and DuPont. Mo Hailong, director of international business at the Beijing Dabeinong Technology Group Co., part of the Beijing-based DBN Group, was accused of stealing trade secrets after he was found digging in an Iowa cornfield.[86]

^A decade of EU-funded GMO research (2001-2010)(PDF). Directorate-General for Research and Innovation. Biotechnologies, Agriculture, Food. European Union. 2010. doi:10.2777/97784. ISBN978-92-79-16344-9. "The main conclusion to be drawn from the efforts of more than 130 research projects, covering a period of more than 25 years of research, and involving more than 500 independent research groups, is that biotechnology, and in particular GMOs, are not per se more risky than e.g. conventional plant breeding technologies." (p. 16)

^FAO, 2004. State of Food and Agriculture 2003–2004. Agricultural Biotechnology: Meeting the Needs of the Poor. Food and Agriculture Organization of the United Nations, Rome. "Currently available transgenic crops and foods derived from them have been judged safe to eat and the methods used to test their safety have been deemed appropriate. These conclusions represent the consensus of the scientific evidence surveyed by the ICSU (2003) and they are consistent with the views of the World Health Organization (WHO, 2002). These foods have been assessed for increased risks to human health by several national regulatory authorities (inter alia, Argentina, Brazil, Canada, China, the United Kingdom and the United States) using their national food safety procedures (ICSU). To date no verifiable untoward toxic or nutritionally deleterious effects resulting from the consumption of foods derived from genetically modified crops have been discovered anywhere in the world (GM Science Review Panel). Many millions of people have consumed foods derived from GM plants - mainly maize, soybean and oilseed rape - without any observed adverse effects (ICSU)."

United States Institute of Medicine and National Research Council (2004). Safety of Genetically Engineered Foods: Approaches to Assessing Unintended Health Effects. National Academies Press. Free full-text. National Academies Press. See pp11ff on need for better standards and tools to evaluate GM food.